Marketable Securities - Summary of Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Marketable securities available-for-sale
Amortization Cost	$ 143,415	$ 60,584
Gross Unrealized Gains	35
Gross Unrealized Losses	(9)	(8)
Estimated Fair Value	143,441	60,576
U.S. Treasury obligations
Marketable securities available-for-sale
Amortization Cost	143,415	60,584
Gross Unrealized Gains	35
Gross Unrealized Losses	(9)	(8)
Estimated Fair Value	$ 143,441	$ 60,576

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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